Vacuum-pump.



Patented Oct. 24, I899. E. F. DWYER. I VACUUM PUMP.

(Application filed. May 21, 1898.)

2 Sheets- Sheet (No Model.)

L [LE] Patented Oct. 24,1399. E. F. nwvsn.

vAcuum PUMP. (Application filed May 21 1898.)

(No Model.)

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- UNITED STATES PATENT @EETQE.

ELMER F. DWYER, OF LYNN, MASSACHUSETTS.

VACUUM-PUMP.

SPECIFICATION forming part of Letters Patent No. 63 5,375, dated October 24?, 1899.

Application filed May 21, 1893. Serial No. 681.386. (No model.)

To all whont it may concern:

Be it known that I, ELMERF. DWYER, a citizen of the United States, residing at Lynn, in the county of Essex and State of Massachusetts, have invented certain new and useful Improvements in Vacuum-Pumps; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to that class of mechanically-operated pumps designed for the exhaustion of air and the production of a high vacuum in incandescent lamps, Crookes tubes, or other apparatus requiring the highest or most perfect vacua.

By mechanically-operated pumps I refer to those pumps having a piston and cylinder relatively movable as distinguished from pumps employing mercury or liquids, the movements of which accomplish the removal of air or gase'ssuoh, for instance, as the socalled Geissler or Sprengel pumps, now well known.

The object of my invention is to secure a simple pump of such form that it shall require in operation little attention and shall not be liable to easydisarrangement and capable of automatically preserving itself in efficient working condition, by which I am enabled to produce ahigher degree of vacuum in a shorter time thanhas hitherto been possible and which is apractical machine particularly adaptedfor daily use in factories where high vacua are required, such as incandescent-lamp factories.

In the accompanying drawings I have illustrated the preferred form of my invention, wherein-- Figure 1 is a front elevation of the pump with the pump-cylinder and the associated parts of one side of the machine shown in cross-section. Fig. 2 is a cross-section of my oil-trap. Fig. 3 is a side elevation of the pump. Fig. 4 is a vertical section of the cylinder, taken at right angles to the section shown in Fig. 1. Fig. 5 is an enlarged view in cross-section of the cylinder and piston, showing a modification.

Upon the base B are mounted two vertical standards S S which may be integral with At the top is a yoke Y to secure I prefer to mount the base. and stiffen the standards.

twopumps upon this frame on opposite sides of the cylinder and to drive them from one main driving-shaft. Inasmuch as these pumps are duplicates of each other, except as hereinafter .noted, a description of one will serve for both.

Between the two standards and near the base I support a heavy driving-pulley W, by which power is applied to the machine. This pulley is mounted upon the shaft X, supported in suitable journals in the standards. Upon the opposite ends of the shaft are mounted cranks A A which carry boxes sliding in slotted cross-heads carried by the piston-rods R R These piston-rods are guided, respectively, by the guides G G and G G As seen in Fig. 1, upon the right upper end of the frame there is supported an exhaustchamber 0, from which depends the pumpcylinder 0. Working in the cylinder is an imperforate piston H, attached in the usual manner to the piston-rod R which fits the cylinder. The vessel or chamber desired to be exhausted is attached to the pipe T, which enters through a port Q into the pump-cylinder. This port opens into the cylinder at thepoint just above the position assumed by the upper end of the piston at the point of its lowermost position in the cylinder.

The exhaust-chamber is connected with the cylinder by means of a Valve-port c, which is normally closed by the valve V. This valve has a long stem R which is supported at its upper end by an opening in the exhaustchamber cover G This cover is provided with a number of openings O and surmounted by an oil-trap. (Bestillustrated in Fig. 2 of the drawings.) The cover is preferably secured to the chamber by screw-threads on its periphery. In the side of the exhaust-chamber and about at its middle is provided an overflow-cock V which connects by an overflowpassage D with the outside of the cylinder and is for the purpose of permitting oil to pass from the exhaust-chamber to the oiljacket, hereinafter to be described, when the oil in the exhaust-chamber shall rise to the level of the cook.

The piston consists of a block provided with packing at its ends of leather or other suitable material held in place by followers, the lower follower being marked F in the draw ings and the upper follower being marked K.

In assembling this piston the lower follower is slid onto the piston-rod until it strikes the shoulder shown at 1. Then the lower packing L'- is put in position. On top of this is placed the piston-body proper, to be followed in turn by the upper packing O and the follower L. The nut N is then screwed onto the end of the piston-rod and firmly secures all the parts together. The upper follower is of the usual form; but the lower follower beyond its ordinary length, where it serves the usual purpose of supporting the packing, is extended downwardly for some distance, the extended portion being reduced in diameter and carrying on its lower end an oil-jacket bottom B An oil-jacket G a little larger in diameter than the cylinder, extends upwardly from the oil-jacket bottom B to which it is fastened by screw-threads or other means.

The lower part of the exhaust-chamber and the space between the piston and the upper end of the cylinder when the piston is in its uppermost position and the oil-jacket and the space around the lower follower inside of the cylinder and extending up to the lower packing are intended to be filled with oil. I prefer for this purpose a non-volatile oil, such as some heavy hydrocarbon oil of the paraflin series, which has been deprived of its volatile constituents by heating it in 'vacuo and in pumping and removing as far as possible any volatile constituents.

In operation the pump being provided with oil, as above described, and the piston being assumed to be at the start at its uppermost position the valve will be in its raised position by reason of the contact with its stem of the upper end of the piston-rod. At this time the oil in the exhaust-chamber and the oil in the cylinder will be in free communication with each other and entirely fill the space above the piston. Now when the piston moves downward it will permit the valve to seatitself, and the further motion of the piston downward will create a vacuum between the oil above the piston and the end of the cylinder. \Vheu the piston shall have moved downward so far as to expose the port Q, the vacuum will draw from the pipe T air or gas sulficient to fill the space above the piston. The length of the piston is such that the port Q, is only uncovered when the piston is at its lowermost position and not at any other time. \Vhen the upward movement of the piston begins, it will first close the port Q, and as it passes upward will reduce the space in which the gas is confined continuously until it has reached the upper limit of its stroke or until the pressure is sufficient to raise the valve from its seat against atmospheric pressure upon the other side thereof, thus affording for it an escape through the exhaust-chamber. \Vhen, however, the gas in the cylinder is extremely rarified, it will never be compressed sufficiently to raise the valve, and in such case the positive opening of the valve at the end of the stroke by the contact therewith of the piston-rod will open the cylinder to the exhaust-chamber, and the gas in the form of bubbles will escape upward, floating through the oil in the valve-port v and exhaust-chamber. This operation is materially assisted by relieving the air-pressure in the exhaust-chamber, as hereinafter described. The air will then find an outlet through the openings in the exhaust-chamber cover and the oil-trap. In the operation of pumping some oil will pass from the oil-jacket on the air side of the piston to the cylinder above the piston, owing to the pressure of the atmosphere on the oil in the jacket and the absence of pressure upon the upper or vacuum side of the piston. The oil thus carried to the upper side of the piston will find an outlet through the valve-port into the exhaustchamber, where, as before suggested, when it shall rise above the level of the overfiow, it will pass through it and the overflow-passage down to the outside of the cylinder and into the oil-jacket.

The oil-trap above referred to consists of an outside shell 0 open at its top and bottom and provided with a central diaphragm, which diaphragm has a large opening I in its center and small holes 0 around its circumference. Over this opening is a small shell C with solid side walls and openings in its top and bottom. Outside of the small shell 0 is carried an intermediate shell 0', which is provided with solid side walls and top and a perforated ring at the bottom by which it is attached to the small shell. In size it is smaller than the outside shell G and larger than the inside shell C The air or gas as it rises through the opening in the exhaustchamber cover carries with it entrained oil. Passing through the opening 0 in the upper end of the inside cylinder it deposits its oil upon the walls of the intermediate cylinder, and the oil flows down through the opening 0 into the outside shell and through the holes 0 in the diaphragm, and so back into the exhaust-chamber,while the air passes downward through the holes 0 and out through the open end of the outside cylinder to the air. This arrangement requires but one valve to be opened and shut. That valve is opened by positive motion and closed by atmospheric pressure in such a manner as to absolutely prevent a passage by it of air. There is no space or clearance at the end of the stroke of the pump-piston, but all the aircontained in the cylinder is forced out by the oil. The separation of the oil and air is accomplished by gravity, the air passing upward through the oil. Moreover, the trap thoroughly prevents the air from carrying any entrained oil to the atmosphere.

The pump thus described is the one shown on the right hand of Fig. 1, which exhausts into the atmosphere. I have found it expedient to employ two pumps in series and to connect the exhaust-chamber of one pump with the cylinder of the other pump. This arrangement is illustrated in the drawings and is adapted for the production of high vacua. The pump P is directly connected with the chamber to be exhausted, and the gases exhausted from it all pass into its exhaustchamber. This chamber must of course be closed from the atmosphere and is provided with an expansion-chamber U on top of it, which is hermetically sealed and connected by small openings with the exhaust-chamber. The maintenance of a vacuum in the exhaust-chamber of the pump P will cause, when the exhaustion of the chamber has commenced, the sudden expansion of the large volume of gas then drawn in, and if the chamber into which it flowed is small, it will expand into that chamber with explosive force. By making the chamber considerably larger this action is in a large measure prevented; but after the exhaust-ing of the chamber to be exhausted has progressed far enough to have removed the major part of the gas contained thereina small quantity only of gas will pass through the valve-port Q) at each reciprocation of the piston, and at such times the escape of the bubbles of gas into the exhaust-chamber will be expedited by reason of the larger size of the bubble due to the low pressure in the exhaust-chamber, whereby the bubble will displace a correspondingly large Volume of the oil.

The overflow-cock in the exhaust-chamber of pump P must normally be closed. At intervals when the oil in the exhaust-chamber shall have accumulated to such an extent as to make it necessary to draw off the surplus and at a time when the pumpis not exhausting the cock will be open and the surplus oil permitted to flow down into the oil-jacket. Under normal conditions the cylinder of the pump 1? will be connected by the pipe T with the upper end of the exhaust-chamber of the pump P. In this way it will be seen that the principal result accomplished by the use of the second pump will be to keep the oil in the first pump free from air and gases by entirely separating it from the airand by constantly removing any volatile constituents of the oil.

For the production of very perfect vacua such, for instance, as would serve for exhausting incandescent lampsI prefer to make a slight modification by placing an auxiliary packing between the cylinder and the oil-jacket. The object of this addition is to prevent, as far as possible, the contact of the oil with the outer air and the taking up of watery vapors therefrom, which interfere with the most efficient operation of the pump. The cylinder is provided with a leather or metallic packing-ring, which engages the inner surface of the oil-jacket. This modification is illustrated in Fig. 5 of the drawings, wherein the ring is represented by the reference-letter a and the check-valve therein by the reference-letter b. An oil seal is maintained above the check-valve. Below the ring it will be seen that when the piston and oil-jacket descend there will be formed a vacuum above the piston and a vacuum below the packing-ring. Now the particular virtue in this resides in the fact that it serves to balance the pressures upon the opposite sides of the piston, whereby the tendency to force oil from the air side of the piston to the vacuum side of the piston is largely overcome and the flow of the oil in that direction almost entirely stopped.

While I have thus described the preferred form of embodiment of my invention, it isto be understood that I do not limit myself to this precise means, but consider that my invention broadly contemplates any construction of vacuum-pump wherein the cylinder on the air side of the piston is provided with means carried by the piston-rod for maintaining a liquid packing in the cylinder. It is within the purview of my invention to apply such means to anyform of vacuum-pump. I have named oil as the liquid for packing the cylinder on the air side of the piston and the exhaust-valve; but it is obvious that any other suitable fluid is within the scope of my invention.

Having thus described the construction and mode of operation, What I claim as new, and desire to protect by Letters Patent of the United States, is-

1. In a vacuum pump, the combination with a cylinder, piston fitting the cylinder and piston-rod, of means carried by the piston-rod for liquid-packin g the cylinder on the air side of the piston, substantially as described.

2. In a vacuum -pump, the combination with a cylinder, piston and piston-rod, of means carried by the piston fitting the cylinder-rod for maintaining liquid packing against the air side of the piston, substantially as described.

3. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of an imperforate piston fitting said cylinder, a piston-rod and means carried by the piston-rod for maintaining a liquid packing in said cylinder on the air side of said piston, substan tially as described.

4. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of an imperforate piston fitting said cylinder, a piston-rod, and means carried by the piston-rod for maintaining liquid against the air side of the piston, substantially as described.

5. In a vacuum -pump, the combination with a cylinder, provided with admission and exhaust ports and an exhaust-valve, of a piston, a piston-rod, means carried by the piston-rod for maintaining liquid against the air side of the piston, and means for maintain- ICC ing liquid around the exhaust-valve whereby the piston and exhaust-valve are packed with liquid, substantially as described.

6. In a vacuum -pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of a piston, a piston-rod, and means carried by the piston-rod for maintaining liquid against the air side of the piston, and an exhaust-chamber adapted to contain liquid to pack the exl1aust-valve, substantially as described.

7. In a vacuum pump, the combination with a cylinder provided with admission and exhaust ports, and an exhaust-valve, of a piston, a piston-rod, means carried by the piston-rod for maintaining liquid against the air side of the piston, an exhaust-chamber adapt= ed to contain liquid to pack the exhaust-valve, and means for conducting surplus liquid from the exhaust-chamber to the means for maintaining liquid against the air side of the piston, substantially as described.

8. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of an imperforate piston fitting said cylinder, a piston-rod, means carried by the piston-rod for maintaining liquid against the air side of the piston, an exhaust-chamber adapted to contain liquid to pack the exhaust-valve, and means for conducting surplus liquid from the exhaust-chamber to the air side of the piston, substantially as described.

9. In a vacuum -pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of a piston, a piston-rod, means carried by the pistonrod for maintaining liquid against the air side of the piston, an exhaust-chamber, and means for exhausting the exhaust-chamber, substantially as described.

10. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of a piston, a piston-rod, means carried by the pistonrod for maintainingliquid against the air side of the piston, and means for preventing the access of atmospheric air to the liquid maintained against the air side of the piston.

11. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of a piston, a piston-rod, means carried by the pistonrod for maintaining liquid against the air side of the piston, means for preventing the access of atmospheric air to the liquid maintained against the air side of the piston, an exhaust-chamber, and means for exhausting the exhaustchamber, substantially as described.

12. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of a piston, a piston-rod, means carried by the pistonrod for maintaining liquid against the air side of the piston, means for preventing the access of atmospheric air to the liquid maintained against the air side of the piston, an exhaust-chamber, adapted to contain liquid to pack the exhaust-valve, means for conducting surplus liquid from the exhaustchamber to the means for maintaining liquid against the air side of the piston, and means for exhausting the exhaust-chamber, substantially as described.

13. In a vacuum-pump, the combination with a cylinder open at one end and closed at the other provided with an admission port in its side and an exhaust-port in its closed end, of a piston, a piston-rod, an exhaust-valve normally closing said exhaust-port, the piston being adapted by its movement to open the admission and exhaust ports respectively at the ends of its reciprocations, and means carried by the piston-rod for maintaining liquid against the air side of the piston, the cylinderclearance being adapted to be filled with liquid and the exhaust-valve being adapted to be packed with liquid, substantially as described.

M. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of an imperforatc piston fitting said cylinder, aliquich jacket surrounding the cylinder and carried by the piston for maintaining liquid against the air side of the piston, substantially as described.

15. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of an imperforate piston fitting said cylinder, a liquidjacket surrounding said cylinder and carried by the piston, whereby the piston is packed with liquid and an exhaust chamber for maintaining liquid around the exhaust-valve, whereby the exhaust-valve is packed with liquid, substantially as described.

16. In a vacuum-pump, the combination with a cylinder, provided with admission and exhaust ports and an exhaust-valve, of an imperforate piston fitting said cylinder, a liquidjacket surrounding said cylinder and carried by the piston, whereby the piston is packed with liquid, an exhaust-chamber for maintaining liquid around the exhaust-valve, the said exhaust-chamber being provided with an overflow-outlet to the said liquid-jacket, substantially as described.

17. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports and an exhaust-valve, of an imperforate piston fitting said cylinder, a liquidjacket surrounding said cylinder and carried by the piston, whereby the piston is packed with liquid, a packing-ring interposed between the cylinder and the liquid-jacket for preventing the access of atmospheric air to the liquid in the liquid-jacket, an exhaustchamber adapted to be partially filled with liquid to pack the exhaust-valve therewith and means for exhausting the exhaust-chamber, substantially as described.

18. In a vacuum-pump, the combination with a cylinder provided with admission and exhaust ports andan exhaust-valve, of an imperforate piston fitting said cylinder, a liquidjacket surrounding said cylinder and carried by the piston, whereby the piston is packed with liquid, a packing-ring interposed between the cylinder and the liquid-jacket for preventing the access of atmospheric air to the liquid in the liquid-jacket, an exhaustchamber adapted to be partially filled with liquid to pack the exhaust-valve therewith, means for exhausting the exhaust'chamber and means for conducting surplus liquid from the exhaust-chamber to the liquid-jacket,substantially as described.

19. In a vacuum-pump, the combination with a cylinder, open at one end and closed at the other provided with an admission-port in its side and an exhaust-port in its closed end, of an imperforate piston fitting said cylinder and an exhaust-valve normally closing said exhaust-port, a liquid-jacket surrounding said cylinder and carried by the piston, whereby the piston is packed with liquid, and an exhaust-chamber for maintaining liquid around the exhaust-valve, the cylinder'clearance being filled with liquid and the piston being adapted by its movement to open the admission and exhaust ports respectively, at the ends of its reciprocation s, substantially as described.

20. In a vacuum-pump, the combination with a cylinder and its piston, of an oil-jacket attached to the piston and surrounding the cylinder, and a packing-ring interposed between the cylinder and oil-jacket, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

ELMER F. DWYER.

Witnesses:

T. HART ANDERSON, A. E. WHYTE. 

